Adrenal chromaffin cells contain high affinity saturable benzodiazepine and GABA binding sites. The pharmacological specificity and the interaction between these two binding sites is similar to that reported in brain. However, the benzodiazepine binding sites of adrenal medulla cells fail to bidn beta-carbolines. Preliminary results suggest that diazepam and muscimol change the release of enkephalin-like material from primary culture of bovine adrenal medullary cells.